Glabracins A and B, two new acetogenins from Annona glabra

Two new bioactive bis-THF Annonaceous acetogenins, glabracins A (1) and B (2), and two previously known acetogenins, javoricin (3) and bullatanocin (4), have been isolated from the leaves of Annona glabra by activity-directed fractionation using the brine shrimp lethality test (BST). The structures of 1 and 2 were elucidated based on spectroscopic and chemical methods, and the absolute stereochemistries were partially determined by the advanced Mosher ester method. 1 and 2 showed selective cytotoxicities to certain human tumor cell lines, and 1 was significantly more potent although 1 and 2 differ only in the stereochemistry of their vicinal diols at C-23/24.